I've a big problem getting my clients connected to the internet over dsl. What I have so far is a working dsl connection on external side (pppoeconf and pon dsl-provider). I changed the mysql entry describing the network devices and I can see the ppp0 connection details on web-admin/network. But none of my clients is able to reach the outside world. The firewall rules are untouched.

In my setup the core's resolv.conf has ips of the domain servers handed out by my modem's DHCP (which are my provider's dns and the modem's ip). The diskless MD has the ip of the core as it's nameserver. I hope that helps.

Even without domain resolution, you can always try to ping/traceroute ip numbers directly.